Re: [PATCH RFC 05/11] rust: sync: Add dummy LockClassKey implementation for !CONFIG_LOCKDEP

Martin Rodriguez Reboredo
2023-07-14T20:37:56Z

On 7/14/23 06:13, Asahi Lina wrote:
> Lock classes aren't used without lockdep. The C side declares the key
> as an empty struct in that case, but let's make it an explicit ZST in
> Rust, implemented in a separate module. This allows us to more easily
> guarantee that the lockdep code will be trivially optimized out without
> CONFIG_LOCKDEP, including LockClassKey arguments that are passed around.
>
> Depending on whether CONFIG_LOCKDEP is enabled or not, we then import
> the real lockdep implementation or the dummy one.
>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---
> rust/kernel/sync.rs | 29 ++++++++---------------------
> rust/kernel/sync/lockdep.rs | 27 +++++++++++++++++++++++++++
> rust/kernel/sync/no_lockdep.rs | 19 +++++++++++++++++++
> 3 files changed, 54 insertions(+), 21 deletions(-)
>
> diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
> index d219ee518eff..352472c6b77a 100644
> --- a/rust/kernel/sync.rs
> +++ b/rust/kernel/sync.rs
> @@ -5,37 +5,24 @@
> //! This module contains the kernel APIs related to synchronisation that have been ported or
> //! wrapped for usage by Rust code in the kernel.
>
> -use crate::types::Opaque;
> -
> mod arc;
> mod condvar;
> pub mod lock;
> mod locked_by;
>
> +#[cfg(CONFIG_LOCKDEP)]
> +mod lockdep;
> +#[cfg(not(CONFIG_LOCKDEP))]
> +mod no_lockdep;

Some care must be taken wrt how is it going to appear in the resulting
documentation, I think it can lead to missing details. `#[cfg(doc)]`
should be considered.

> +#[cfg(not(CONFIG_LOCKDEP))]
> +use no_lockdep as lockdep;
> …